With rapid increase of network traffic and bandwidth, operators have increasingly urgent requirements on intelligent scheduling functions of underlying wavelength division networks. Therefore, reconfigurable optical add/drop multiplexers (ROADM) are gradually adopted in an increasing number of high-end operators' networks. After the ROADM is introduced into a network, an operator can provide a wavelength-level service soon, thereby facilitating network planning to reduce operation costs, and facilitating maintenance to reduce maintenance costs.
On the other hand, in an optical communications long-haul transmission network, optical-electrical-optical (OEO) conversion in a link of a system tends to be reduced. Therefore, it becomes increasingly difficult to convert an optical signal to an electrical signal and then detect a bit error rate of a transmitted signal at an electrical layer, and testing the bit error rate only on a termination of the link is disadvantageous to fault locating. With an increased transmission capacity and improved flexibility in an optical network, system complexity becomes higher. To effectively control and manage the optical network, it becomes more important to monitor an optical signal for high-speed dense wavelength division multiplexing (DWDM) in the network.
Optical signal monitoring covers a plurality of aspects. For example, optical power monitoring can reflect a basic working status of a channel and instruct a system to perform automatic power equilibrium; optical signal-noise-ratio (OSNR) monitoring can relatively accurately reflect signal quality; dispersion monitoring can reflect a dispersion status of the channel to instruct the system to perform dispersion compensation on an optical layer or an electrical layer. These parameters are important for optical performance monitoring, facilitate impairment suppression, fault locating, degradation detection, backup, and recovery of the optical network, and are beneficial to stable working of the optical network. Optical signal monitoring is indispensable to all important network elements in the network. Therefore, it is very necessary to monitor a transmitted signal in real time by using an ROADM site.
A wavelength selective switch (WSS) is a technical option of current ROADM. For a 1×N WSS, 1 refers to a common (COM) port, and N represents branch ports. Operation of the WSS is as follows: When a group of wavelength division multiplexing (WDM) signals enter from the COM port, the group of WDM signals are separated based on optical wavelengths, and then each wavelength is routed to one of the N branch ports based on a system requirement. Oppositely, an optical signal can be received, as input, from the N branch ports, and can be sent, as output, from the COM port.
An LCoS-WSS-based signal monitoring solution is provided in the prior art. In this solution, a single flare on a liquid crystal on silicon (LCoS) is divided into an optical monitoring area and a WSS signal switching area for separate processing. For example, if a flare occupies 200 pixels in total in a direction of an output port, 20 of the 200 pixels may be designated as the optical monitoring area, and the remaining 180 pixels are designated as the WSS signal switching area.
However, in the foregoing solution in the prior art, when monitored light is processed, phase information of the LCoS also needs to be continuously updated, to obtain different wavelength channels through filtering in a time-sharing manner for detection and monitoring. A scanning update speed of the LCoS is usually approximately 100 ms. If 80 channels in a band C need to be scanned, a time period of approximately 10 s is required. For an N×M WSS device including a plurality of ports, a longer time period is required, and a demand for quick fault locating in a future network cannot be satisfied.